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Dear Bernhard, further thinking about the Babinet scaling effects, I have to correct my conclusion in the last sentence: On 12.01.2015 14:21, Dirk Kostrewa wrote: > If, however, the unmodelled part is less well ordered (which is the > more common case), it's contribution will mainly affect the model's > Fcalc at low resolution. If the overall scaling is dominated by the > high resolution terms (which is usually the case), the unmodelled part > will not have an effect on the overall scale factor of the model's > Fcalc, leaving only the Fcalc at low resolution somewhat too low. > Since lowering the model's Fcalc scale factor at low resolution is the > main purpose of the Babinet solvent correction, this will lead to an > _underestimation_ (!) of the Babinet bulk solvent contribution scale > factor (ksol). This, in principle, should increase, or overestimate, > the signal of the difference densities at low resolution, which might > also help with interpretation of the unmodelled part. The underestimation of the Babinet bulk solvent scale factor is equivalent to an overestimation of the contrast between protein and solvent and should therefore lead to an overestimation of the Fcalc at low resolution. If scaling is still dominated by the high resolution terms, this should lead to a decrease, or underestimation, of the structure factor differences at low resolution, which would reduce the overall signal of the difference densities. But still, this will be an overall effect and not restricted to the location of the unmodelled part. Best regards, Dirk. -- ******************************************************* Dirk Kostrewa Gene Center Munich, A5.07 Department of Biochemistry Ludwig-Maximilians-Universität München Feodor-Lynen-Str. 25 D-81377 Munich Germany Phone: +49-89-2180-76845 Fax: +49-89-2180-76999 E-mail: [log in to unmask] WWW: www.genzentrum.lmu.de *******************************************************